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Old Mar 15, 2012, 07:58 AM
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dle 20cc and 4blade prop

does anyone know if i can spin a 4 blade prop with a dle 20. Does it have enough tq to generate enough rpm to give me enough thrust. Id like to run a 4 blade for scale performance on my new P-51 hangar 9 blue nose?
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Old Mar 15, 2012, 11:41 PM
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You can run a 4 blade prop on any motor. Rule of thum says that if you run a 3 blade you go down an inch in diameter over a 2 blade and for a 4 blade you would drop another inch on the diameter.
So if your DLE20 can turn a 17x6 2 blade at 8000 rpm you would probable get the same rpm with a 15x6 4 blade.
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Old Mar 16, 2012, 06:41 AM
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The drop a inch rule does not work as well as you go into bigger prop sizes and displacements, also the make of 3/4 blade is a major factor, you may spin a crap mas 16 8 3 at reasonable rpm but I can tell you that a 15 8 3 graupner will loose a little thrust and rpm over a 17 6 xoar. And a graupner 16 8 3 will be in the 7400 rpm range, 1000 rpm down. A 4 blade 15 8 4 mas might yeild good results as said above.

The dle will turn them all btw, but performance will differ vastly.
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Old Mar 16, 2012, 06:58 AM
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yea i was looking at the zinger wood 4 blade props they seem to be reasonable priced and have alot of options for length and pitch.

I think idea would be a 17x8 or 18x8 so should i run a 16x10 4 blade or step into a 15x10 4 blade Im still new on props and stuff. I have the length and pitch figured out but the whole 3 blade and 4 blade thing. I know a 3 and 4 blade take away top end speed but they also add thrust to the prop making it easier for take offs
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Old Mar 16, 2012, 08:40 AM
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First thing you need to find out is what 2 blade prop the DLE20 will turn and then definetly go done by 2 inchs in diameter. Then you can put some figures into this web calculator.
http://personal.osi.hu/fuzesisz/strc_eng/index.htm
I've found it to be quite helpfull in selecting props.
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Old Mar 16, 2012, 03:28 PM
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gotcha the max prop i think the 20 can turn is a 18x8 ive seen people run before so i should go to a 16x8 and go from there correct
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Old Mar 16, 2012, 05:18 PM
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Forget the 16 8 4 unless that is the crappest prop ever made it should be to much for the dle 20. Go with the 15 8 4, if the zingers are as crap as they say you may get away with this size. 18 8 on a dle 20, no chance in the real world.
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Old Mar 16, 2012, 06:40 PM
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ok. where can you find the zinger 4 blade props at. I did some searching and i could not find any but the 20x10 4 blade. Are they special order from local hobby shop or can they be found online somewhere??
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Old Mar 16, 2012, 08:55 PM
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DLE recommend a few different props but in the midle is a 16x6 or 15x8. Had a bit of a look around in forums and one guy has a 17x6 turning 8600 rpm for 3D. I guessing as you have a war bird you would want the 16x8 2 blade to give a bit more speed.
If you look on the Zinger page.
http://www.zingerpropeller.com/index.htm
Their conversion says you would use a 14x8 4 blade.
If it would turn at 8600 rpm that should give you 14lbs of thrust at 65 mph, that would be heaps for a 60 size bird.
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Old Mar 17, 2012, 05:22 PM
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well from what i read a 4 blade should give you double the thrust of a 2 blade would do. or at least more thrust than a 2 blade. but loose top speed
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Old Mar 18, 2012, 03:59 AM
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Quote:
Originally Posted by chaos2984 View Post
well from what i read a 4 blade should give you double the thrust of a 2 blade would do. or at least more thrust than a 2 blade. but loose top speed
That would only be the case with the same diameter. But your motor only has a limited amout of power so going down 2" in diameter will even things out.
Have a play with the "Static thrust calculator" I posted before.
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Old Mar 18, 2012, 06:22 AM
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gotcha. will do that. But where can i find someone who carries all zinger 4 blade props. All i can find is the 20x10x4
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Old Mar 18, 2012, 06:33 AM
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well looking at the prop thrust calculator. Seems like a 15x8 will work for a 4 blade. And what is the cf of the prop mean. Also i back the rpm down to 7900 from 9k max rpm and that gave me 14.4 lbs of thrust with only needing 2.4hp and the engine makes 2.5hp That should be good correct
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Old Mar 18, 2012, 07:01 AM
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It might make 2.5 hp but it would be at 9000 rpm which means you would be down below 2hp at 7900.
15x8 may still fly the plane but I would start with 14x8.
Does Zinger sell to public? Looks like them might from their web site.
Not quite sure about the cf but could have something to do with the friction, I don't worry about it as I'm generaly only using it as a guide.
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Old Mar 18, 2012, 08:31 AM
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If you can turn a 4 blade 15x8 at around 7900rpms with a dle20 then it would be a great flying P-51. A 4 blade 14x8 would give you more rpms though.
I used a 4 blade 15.5x12 on my TF .60 size P-51 using an OS 200FS (around 7200rpms). I think it gained rpms in the air as mine was clocked at 93mph at the field.
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